[MacPorts] #60325: icu 65.1: platform.h has macro clash with cpprestsdk (and possibly other libraries)

[MacPorts]

#60325: icu 65.1: platform.h has macro clash with cpprestsdk (and possibly other
libraries)
-------------------------------------------------+-------------------------
 Reporter:  Lord-Kamina                          |      Owner:  (none)
     Type:  defect                               |     Status:  new
 Priority:  Normal                               |  Milestone:
Component:  ports                                |    Version:  2.6.2
 Keywords:  declspec clang dllimport dllexport   |       Port:  icu
  cpprestsdk                                     |
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 I'll soon make a PR for this because it appears to be a simple fix;
 nonetheless, I figured it would be a good idea to make a ticket here also
 so we can track when it gets fixed upstream (I've already reported it at
 https://unicode-org.atlassian.net/browse/ICU-21064

 In short, in ICU65.1, they introduced macros around Clang's
 `__has_attribute` features. In a few places they use those calls with
 `dllexport`and `dllimport`as parameters, which clashes with macro
 definitions in CppRestSdk. In my case, I noticed this compiling an app
 that uses both CppRestSdk and ICU, which failed with the following error:


 {{{
 In file included from /Users/Koji/performous/game/unicode.hh:6:
 In file included from /opt/local/include/libxml2/unicode/tblcoll.h:65:
 In file included from /opt/local/include/libxml2/unicode/utypes.h:38:
 In file included from /opt/local/include/libxml2/unicode/umachine.h:46:
 In file included from /opt/local/include/libxml2/unicode/ptypes.h:52:
 /opt/local/include/libxml2/unicode/platform.h:818:29: error: too few
 arguments provided to function-like macro invocation
                             UPRV_HAS_DECLSPEC_ATTRIBUTE(dllimport))
                             ^
 /opt/local/include/libxml2/unicode/platform.h:438:69: note: expanded from
 macro 'UPRV_HAS_DECLSPEC_ATTRIBUTE'
 #   define UPRV_HAS_DECLSPEC_ATTRIBUTE(x) __has_declspec_attribute(x)
                                                                     ^
 /opt/local/include/libxml2/unicode/platform.h:843:29: error: too few
 arguments provided to function-like macro invocation
                             UPRV_HAS_DECLSPEC_ATTRIBUTE(dllimport))
                             ^
 /opt/local/include/libxml2/unicode/platform.h:438:69: note: expanded from
 macro 'UPRV_HAS_DECLSPEC_ATTRIBUTE'
 #   define UPRV_HAS_DECLSPEC_ATTRIBUTE(x) __has_declspec_attribute(x)
 }}}


 I'm not entirely sure whose at fault here, ICU or CppRestSdk, but as per
 https://clang.llvm.org/docs/LanguageExtensions.html#has-declspec-
 attribute, enclosing the attributes in double underscores will prevent the
 clash (I tested it, and the error went away, at least)

-- 
Ticket URL: <https://trac.macports.org/ticket/60325>
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